| abstract |
An ultrahigh molecular weight polyethylene stretched microporous film, which comprises at least an ultrahigh molecular weight polyethylene having an intrinsic viscosity ([η]) of at least 7 dl/g and at most 60 dl/g, and which has a porosity of at least 10% and at most 70% and a breaking stress of at least 1 MPa when melt-stretched at 150° C., which uses, as the ultrahigh molecular weight polyethylene, preferably ultrahigh molecular weight polyethylene particles which satisfy (1) an intrinsic viscosity ([η]) of at least 7 dl/g and at most 60 dl/g, (2) a bulk density of at least 130 kg/m3 and at most 700 kg/m3, and (3) ΔTm (ΔTm=Tm1−Tm2) of at least 9° C. and at most 30° C., which is a difference between the melting point (Tm1) at the 1st scanning and the melting point (Tm2) at the 2nd scanning measured by DSC. |